Until recently there were significant differences between the aviation oxygen portable systems offered by Aerox and Nelson and SkyOx. There is, however, precious little to tell them apart these days.

What gives here? Every general aviation oxygen system must include a cylinder, regulator, and delivery equipment. What's going on here? Let's take a looksee...

Click HERE for Cylinder Specs and Aviation Oxygen Duration

Nelson offers three aluminum cylinder - sizes D, E & M.

SkyOx offers four aluminum cylinder - sizes A,C,D and E.

Aerox offers five aluminum cylinders from which to choose - sizes A, C, D, E and M. In addition they sell 11cf and 22cf portable systems using Kevlar Composite cylinders for an additional $900.

Today's generation of portable systems come with an aluminum cylinder because they are 1) lightweight, 2) inexpensive, and 3) have no life limit. They need to be hydro-tested every five years. (The cost for the test will vary, depending on where you take the cylinder - most pilots take their cylinders to a local welding shop - who will most probably send it out to a cylinder supply house for the actual test)

[NOTE: Aerox has larger aluminum, steel or composite cylinders available for purchase for replacement or remote use i.e. not for portable use as they must be secured with clamps.] Steel cylinders have a 15 or 24-year life limit, with a hydro-test required every three or five years and they are quite large. Composite/Kevlar cylinders have a 15 year life limit with hydro-test required every three years. The composite cylinders are significantly lighter than are aluminum or steel - thus the higher cost.

It is generally acknowledged that piston type regulators are more efficient at lower pressure levels, and it has therefore largely replaced the diaphragm-type due the simplicity of construction and unquestioned reliability. The piston type has only one moving part, and it will deliver the designed flow down to less than 50 psi.

Each of these companies uses a Sherwood Regulator. Aerox and Nelson use the piston type which are quite compact and low profile. The diaphragm-style used by Sky Ox is quite large, and it comes with altitude gauge.

Each company offers regulators with up to four ports. Should you wish to add a position at a later date, Aerox offers a simple Y-adapter to be added to any of the four ports (up to eight persons). The SkyOx regulators are not expandable. The 2-place Nelson regulator is expandable to four, but this must be done at the factory.

NOTE: It is important to decide at the outset how many positions you will need, since adding options at a later date is not cost effective with any of these companies.

Both Aerox and Nelson developed their now well-known flow meters which come with dual-index (one for use with the Oxymizer cannula; the other for when converting to a mask over 18,000 ft.).

A drawback of the Nelson Flow meter is that it necessitates the use of three different hose clamps to keep the components (flow meter, tubing and connector) from blowing apart with the high pressure emanating from the regulator. The clamps require a special tool to be taken off or on. In addition, the Nelson reportedly has breakage where the valve stem meets the flow meter, either during flight or storage. Some pilots find that the oxygen flow is inadvertently changed when the in-line needle valve catches on a sleeve or on other equipment.

The Aerox system places their needle valve at the connector where flow reduction takes place and no clamps are needed. Also, the Aerox flow meter fits snugly into the modified tubing ends provided by the Chad Oxymizer.

Pilots need to decide 1) if each passenger can/should be responsible for altitude settings and then to remember 2) to monitor the in-line needle valves to make sure the flow has not inadvertently/accidentally been changed by catching the sleeve on whatever.

Sky Ox does not use a flow meter. They use a flow indicator, which tells you only if the oxygen is on or off, and not how much flow you are getting for what altitude or whether or not your hose is kinked. They regulate the flow of aviation oxygen by the setting the green gauge to .60 liters per minute (there is no reminder or arrow to point to .60). No matter the altitude, this setting remains at .60 liters per minute. It is not changed unless you go over 18,000 feet. At this point you will don a standard mask, and reset the green gauge to the altitude flown instead of .60 liters per minute.

Aerox and Nelson both supply the Chad Oxysaver nasal cannula with their systems. Sky Ox offers the Chad Oxysaver pendant cannula. Each of these cannulas is efficient and has been approved for use up to 18,000 feet over which you must use a standard mask or cannula. Most pilots find the tubing on the pendant cannula to be rather stiff and unyielding, comfort-wise, and the ear loops bug them. The nasal cannula seems to be comfortable and can also be used with a headset or when drinking or eating.

Aerox, Sky Ox and Nelson all use brass plated steel quick-connectors.

Sophisticated cases/harnesses are provided by Aerox and Nelson--and The Airport Shoppe. While all of these cases provides a pouch or pocket which appears to be for storage of the delivery equipment - do not use it for that purpose unless you wish to kink the hoses and intermingle the sneezes and sniffles of the cannulas! At one time the Aviation Consumer touted the Nelson system for having the "superior" carrying case - albeit they did not find their system superior. Since that pronouncement all manufacturers, including us, have provided a deluxe carrying case with pouch and other features - necessary apparently to meet the exacting standards Aviation Consumer. [The Airport Shoppe in addition offers square zippered accessory case with two or four dividers for separating these very personal items. These sell for $42.95 and $49.95. Use the pouches for snacks.]

The Aerox and Airport Shoppe cases are made from the more durable DuPont Ballistic Nylon. The Nelson case is made from DuPont Cordura. Each carrying case fits the corresponding cylinder snugly and offer a separate harness which attaches the cylinder "papoose" to the seatback for safety in flight. The Nelson case has Velcro straps which wrap the neck of the cylinder to secure it during flight or use when the "papoose" is open. The Aerox and Airport Shoppe cases zip up so the regulator is covered during flight for additional safety during turbulence. All harnesses from these companies have strong webbing, buckles and snaps for safety and security of the cylinder.

The SkyOx model is flimsy, poorly padded and has no harness separate from the carrying case. The one handle provided is intended to loop over the seat back--it is then resting diagonally on the back floor--a very undesirable design.

Both Aerox and Nelson enjoy extremely high oxygen duration because their patented needle valves allow precise oxygen flow to be selected for each altitude flown, ranging from .25 liters per minute to .50 liters per minute. SkyOx flow duration is significantly decreased since flow is to be set at a constant .60 liters per minute no matter what altitude is selected for flight.

Click HERE for Cylinder Specs and Aviation Oxygen Duration

These durations are safe only when used with the Oxysaver pendant or nasal cannulas provided. Should the pilot place someone on a regular mask or cannula, the higher altitude index MUST BE SELECTED.

• Nelson: 2-year limited warranty
• Aerox: Limited lifetime warranty
• Sky Ox: One year limited warranty

• Nelson/Precise Flight
• Mountain High